The quality of wooden decks for expensive yachts is very important. Typically, the top surface of these decks is natural teak wood separated with flexible joints (caulk seams) which allow the individual planks of teak (battens & trims) to expand and contract as the wood's moisture content changes with the surrounding environment. These elements (battens, trims and caulking) are always attached to a prepared surface which is normally the same material as the ship's hull. These materials include wood, alloy, steel, fiberglass, or others. This surface is called the “as-built surface” and it must be properly prepared before a teak deck is attached to it. This prepared as built surface is not part of the teak deck. However, the critical joint between these two surfaces, the teak deck and the prepared as built surface is part of the teak deck. In some cases, the teak elements are attached with mechanical fasteners to the surface below and more recently with adhesive only. However, sometimes both fasteners and adhesive is applied to secure the teak deck elements to the prepared as built surface below. Regardless of the method used the desired goal of the current art form of attaching a teak deck to the prepared as built hull surface of a boat, yacht or ship is to provide a permanent, void free, watertight bond between the two surfaces. However, it is a well-known fact that many teak decks are replaced well before the teak wears out. This is often due simply to the fact that a permanent, void free, watertight seal was not achieved between the teak elements and the prepared as built surface during the original installation process. This is distressing since these types of failures normally cause the early removal and replacement of the teak. When replacing an existing teak deck the new teak must be sourced from a limited supply of a rare natural resource.
Teak deck parts are limited in scope and the types of failures well known. The caulking can release allowing water between the caulking and the wood elements. The wood can fail or crack allowing water into the wood to the bottom of the crack. Water can get under the teak deck, between the teak elements and the prepared as built surface if a permanent, void free water bond was not achieved during the construction process. And adhesives and mechanical fasteners can fail for a number of reasons from simply not cleaning the surfaces to improper mixing. There is a clear difference between the normal effects of simple caulk seam failure or a random cracked batten vice the effects of water being trapped under the teak deck. In truth the caulk seams between the individual pieces of teak will fail sooner or later allowing water to seep to the bottom of the seam. It is also normal for a few battens of wood to develop cracks during their life time. There are simply too many seams and too many individual pieces of teak in a teak deck for these elements to remain perfect. When the caulking starts to fail or a random batten cracks on a properly installed teak deck, which has a permanent, void free, water tight bond between the teak elements and the prepared surface below it is not a significant issue. Water slowly working its way down a defective caulk seam or through a crack has no place to go once it reaches a permanent water tight adhesive joint. It is at this permanent, void free, watertight bond holding the teak pieces or teak panels in place that the deck remains structurally sound even if water is in the seams or in cracks in the wood. These water filled seams or water filled cracks of wood do create a problem but one which can easily be remedied by re-seaming the teak deck or replacing a few pieces of defective teakwood. These actions restore the teak deck's water integrity and extend its service life. In other cases, the result of water migrating down through the caulk seams or cracked battens is likely to allow water to penetrate into one of many voids between the teak elements and the prepared hull surface, filling them with water. These voids normally result from a defective installation process, or are created by one of a multitude of possible adhesive failures, or for other reasons.
Any leakage of water from the top surface of a teak deck downward allowing fluid to become trapped in the underlying structure is often catastrophic and can lead to the early structural failure of the entire teak deck necessitating its replacement. This situation can worsen as corrosion of the yacht's structural surfaces can begin. This is due to the fact that “trapped fluid” normally cannot escape, and because fluid is not readily compressible, it is the cause of many teak deck failures. Water trapped in a space under the teak deck acts as a hydraulic fluid when pressure is applied to the top surface (someone stepping on the deck above the area with water filled voids). The water is forced outward creating a larger space in the underlying deck, opening more caulk seams, filling more voids, and causing the teak to further separate from the prepared hull surface. This larger space can now accept more water entering from ever expanding failures. The process often accelerates as water is the world's most common universal corrosive agent: corrosion begins, adhesives fail, fasteners fail, caulking fails, and the teak deck releases. New teak from the rain forest is then required to replace it.
To fully understand the background, a more detailed description of a teak deck's construction is required. The traditional method used for decades by shipwrights around the world is a well-known art and involves planking the deck by independently shaping and attaching each individual strip or batten of wood with mechanical fasteners, some type of adhesive, or both. A newer method was described in U.S. Pat. No. 4,351,256 filed in February of 1980. It involves constructing a teak deck off the boat, using a backing material, and then taking the teak deck in large panels to the yacht for installation. This method is again secured with mechanical fasteners, adhesives or both. In either case the procedure begins with the existing structure or skin of the ship which can be described as the “as-built deck”. An alternate technique for installing teak decks is described in U.S. Pat. No. 7,506,598 issue to Applicant.
As-built decks are normally made of the same material as the ship; i.e., steel, aluminum, fiberglass, epoxy, or wood. Regardless of the material, the as-built deck is almost always uneven and unprotected. Prior to covering it with teak wood, the as-built deck must first be cleaned and protected with some kind of coating or primer to protect it from corrosion and other damage. Following the primer coat (or coats), these uneven decks must be filled with a fairing compound to make them smooth and to make them conform to a desired camber, sheer, and or slope. This will ensure water drains from the finished deck to the desired drain locations. Proper fairing of the as-built deck is critical to ensure the final covering of wood is smooth and that there are no voids underneath it. In fact, improper fairing alone can account for many deck failures as the wood elements could not be properly pressed into the valleys and over the highs of a rolling improperly faired as built surface. One of the reasons to add fairing to an as built surface prior to installing the teak deck is to provide a perfectly smooth surface. For some projects after the fairing is completed, the entire area is covered with plywood to provide cleat stock, insulation, expansion and a more suitable surface to attach a wooden deck. It is easier to glue and screw into plywood than steel, fiberglass or aluminum. This procedure is normally referred to as “sub-decking”. The top of the sub-deck now becomes the prepared as built surface to which the teak deck will be attached. Once the as-built deck has been faired, and or sub-decked to the desired lines (camber and sheer) and smoothness, the final teakwood covering is attached.
The attachment of the teak deck to the prepared hull surface is the most important structural joint affecting the overall life of a teak deck. The attachment techniques used at this critical joint include mechanical fastenings (screws, bolts, or studs), some type of adhesive (polysulfide, polyurethane, silicon, epoxy, etc.), or both mechanical fasteners and adhesives. It is noted that the current trend is away from mechanical fasteners and toward fasten-less teak decks set only in a selected adhesive. Attaching a teak deck without fasteners eliminates the teak plugs and provides for a clean and neat appearance. However, these installation techniques are problematic and it is difficult, but not impossible, to obtain the necessary permanent, void free, and water tight bond critical to give the teak deck a long life. When a teak deck is installed without fasteners, there is no backup to keep the deck in place if the adhesive fails. Therefore, cleaning must be done, adequate adhesive must be applied, adequate evenly applied pressure (with the use of weights, pressure bars, pressure sticks, vacuum, or other means as specified by the adhesive manufacturer), drying times observed; and in all cases careful attention must be paid to the manufacturer's mixing and application instructions. It is critical to properly mix the adhesive, properly apply the adhesive, and use adequate amounts of adhesive. Failure to properly accomplish even one of these steps, or failing to get the adhesive in to the teak deck during its “open” time or applying inadequate or uneven pressure on the teak to press it down into the adhesive are all reasons why many teak decks are completed without permanent, void free, and watertight joints between the bottom of the teak and the prepared as built hull surface. Often this fact goes without notice or it is initially considered acceptable. A new teak deck with new caulking is unlikely to allow water into any voids during the normal 12 to 24 month warranty period. If it is 70 percent attached, it is well-fixed to the hull; and with the assistance of gravity it may remain structurally sound during this period. The fact that it has voids between the teak and subdeck surface is not immediately critical. However in time, sometimes sooner than later, the caulk seams will start to fail or a single batten will crack allowing water into these voids. This is when problems will present themselves. At this point, the teak deck begins to immediately show signs of structural failure and the process of structural damage to the hull begins. The current art of repair is to replace the caulking or replace the defective wood in an attempt to re-establish the watertight integrity of the overall teak deck. Often the most defective area is ripped out and replaced. Little attention has been given to a method or system to correct the real structural issue. These are the voids between the teak and the prepared hull which allows a place for water to trap and destroy the deck through hydraulic action.
What is needed is a better method for repairing teak decks having water trapped in voids between the teak deck and the as-built surface.